Speciation Of Trace Elements Research Articles

Development of a new automated speciation analyser – result of an international interdisciplinary co-operation between scientific and industrial partners

The importance of monitoring trace-element species is increasingly recognised. Such methods are needed for risk assessment of many potentially hazardous substances, such as methylmercury and tributyltin, for example for environmental or food control, medicine or workplace monitoring. Atomic spectrometric techniques alone are incapable of determining elemental species directly, because the relevant information about oxidation or metal-binding state is lost in the atomisation step. As a result, these methods must be combined with separation techniques in order to obtain methods that are highly sensitive as well as species selective. To develop new analytical methods and procedures for element speciation interdisciplinary research is essential. Accordingly, an international interdisciplinary consortium was formed to develop the new automated speciation analyser (ASA). Analytical chemists and physicists from several European institutes and two industrial companies co-operated in this project. As a result, the continuous exchange of scientific results and practical experience, combined with consideration of the needs of routine analytical laboratories, led to the development of an industrial prototype for trace-element speciation.

Multidimensional approaches in biochemical speciation analysis.

An understanding of the mechanisms controlling the essentiality and toxicity of trace elements in biological systems at the molecular level depends critically on the possibility of the identification, characterization, and quantification of chemical forms of these elements involved in life processes. Hyphenated techniques based on the combination of (electro)chromatography with ICP MS have become a routine tool for the analysis for metallospecies present in biological tissues. Finer analytical information on the true (down to individual species) speciation of trace elements in living organisms can be obtained by adding additional dimensions to the separation and detection steps, consisting of a sequential use of different HPLC separation mechanisms and capillary electrophoresis at the separation level, and of the use of electrospray MS, including collision induced dissociation MS, on the detection level. The value of the instrumental analytical data is decisively enhanced by the complementary use of molecular biology approaches involving gene identification, cloning and in vitro reproduction of the metal-controlled processes. A brief summary of the recent progress in biochemical speciation analysis is presented in the context of the latest research carried out in the authors' laboratory.

Multielement trace-element speciation in metal-biomolecules by chromatography coupled with ICP-MS.

The state-of-the-art of multi-element speciation in biological materials by hybrid techniques with inductively coupled plasma-mass spectrometric (ICP-MS) detection is critically reviewed with special attention to multi-metal speciation in metallothioneins (MT) and metallothionein-like proteins (MLP). The most common separation techniques used for the purpose include conventional size-exclusion chromatography (SEC) (with off-line detection) and anion-exchange (AE) or reversed-phase (RP) HPLC coupled on-line to ICP-MS. Advantages and limitations of the different commercial element-selective ICP-MS detectors, including the quadrupole (Q), double focusing (DF), and time-of-flight (TOF) mass analysers, are discussed. Procedures reported for speciation analysis, by use of hybrid techniques, for multi-metal speciation in mussel MLP and rabbit liver MT are illustrated with special emphasis on work performed in the authors' laboratory.

Quantitative Zn speciation in a contaminated dredged sediment by μ-PIXE, μ-SXRF, EXAFS spectroscopy and principal component analysis

Dredging and disposal of sediments onto agricultural soils is a common practice in industrial and urban areas that can be hazardous to the environment when the sediments contain heavy metals. This chemical hazard can be assessed by evaluating the mobility and speciation of metals after sediment deposition. In this study, the speciation of Zn in the coarse (500 to 2000 μm) and fine (<2 μm) fractions of a contaminated sediment dredged from a ship canal in northern France and deposited on an agricultural soil was determined by physical analytical techniques on raw and chemically treated samples. Zn partitioning between coexisting mineral phases and its chemical associations were first determined by micro-particle-induced X-ray emission and micro-synchrotron-based X-ray radiation fluorescence. Zn-containing mineral species were then identified by X-ray diffraction and powder and polarized extended X-ray absorption fine structure spectroscopy (EXAFS). The number, nature, and proportion of Zn species were obtained by a coupled principal component analysis (PCA) and least squares fitting (LSF) procedure, applied herein for the first time to qualitatively (number and nature of species) and quantitatively (relative proportion of species) speciate a metal in a natural system. The coarse fraction consists of slag grains originating from nearby Zn smelters. In this fraction, Zn is primarily present as sphalerite (ZnS) and to a lesser extent as willemite (Zn 2SiO 4), Zn-containing ferric (oxyhydr)oxides, and zincite (ZnO). In the fine fraction, ZnS and Zn-containing Fe (oxyhydr)oxides are the major forms, and Zn-containing phyllosilicate is the minor species. Weathering of ZnS, Zn 2SiO 4, and ZnO under oxidizing conditions after the sediment disposal accounts for the uptake of Zn by Fe (oxyhydr)oxides and phyllosilicates. Two geochemical processes can explain the retention of Zn by secondary minerals: uptake on preexisting minerals and precipitation with dissolved Fe and Si. The second process likely occurs because dissolved Zn and Si are supersaturated with respect to Zn phyllosilicate. EXAFS spectroscopy, in combination with PCA and LSF, is shown to be a meaningful approach to quantitatively determining the speciation of trace elements in sediments and soils.

Mineralogical distribution of trace platinum-group elements in the disseminated sulphide ores of Noril'sk 1 layered intrusion

The mineralogical distribution of Pd, Rh and Ru was determined in three small samples of disseminated ore from the layered Medevezhiy Ruchei Ni–Cu–platinum-group element mine, Noril'sk 1 layered intrusion, Siberia. The three samples were taken from a cross-section of the deposit ranging from the uppermost part of the picrite horizon (chill zone) through the main picrite horizon to the lower taxitic gabbro dolerites. Different microanalytical techniques were used to determine the major- and trace-element species as well as the abundance of major, minor and trace minerals. The results indicate that Pd is concentrated mostly in pentlandite and less in the platinum-group minerals (PGM). In the uppermost part of the picrite horizon about 67% of the Pd occurs in pentlandite, whereas only 30% occurs in the PGM. About two-thirds of the Rh is found in pyrrhotite; the second carrier of importance for Rh is pentlandite. The Ru distribution is more variable between the three samples, but about one-third of the Ru is carried by pentlandite, the remainder being distributed in variable amounts in pyrrhotite, chalcopyrite and pyrite. Knowledge of the platinumgroup element distribution is important for economic evaluation of the mineralization and for efficient metal recovery.

Fractionation of phosphorus and trace elements species in soybean flour and common white bean seeds by size exclusion chromatography–inductively coupled plasma mass spectrometry

Soluble species of phosphorus, sulfur, selenium and eight metals (Mn, Fe, Co, Ni, Cu, Zn, Mo and Cd) in soybean flour and common white bean seeds were investigated by size exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP-MS). Samples were extracted by 0.02 mol l −1 Tris–HCl buffer solution (pH 7.5). Fractionation of sample extracts by preparative scale SEC was accomplished using a Fractogel EMD BioSEC column (600×16 mm) and 0.02 mol l −1 Tris–HCl buffer solution (pH 7.5) as mobile phase (flow rate: 2 ml min −1). A 2-ml sample was injected. Contents of elements in chromatographic fractions were determined by AAS, ICP-AES and ICP-MS. The elution profiles of P, Fe, Co, Ni, Cu, Zn and Mo in both samples were similar. Main species of Co, Ni, Cu, Zn and Mo were found in the low molecular weight region (2–5 kDa), whereas Fe is predominantly bound to high molecular weight compounds (180 kDa). The dominant phosphorus fraction was detected in the medium molecular weight region (10–30 kDa) and the other fraction in the low molecular weight region. Isotachophoretic analysis of chromatographic fractions revealed that the main phosphorus compound in the medium molecular weight region is phytic acid. SEC on Superdex 75 and Superdex Peptide columns (300×10 mm) was performed in on-line hyphenation with ICP-MS. The same mobile phase was used with a flow rate of 0.5 ml min −1; volume of injected sample was 200 μl. Element specific chromatograms were obtained by continuous nebulization of effluent into ICP-mass spectrometer measuring intensities of 47(PO) + and 48(SO) + oxide ions and 55Mn, 57Fe, 59Co, 62Ni, 65Cu, 66Zn, 82Se, 95Mo and 114Cd nuclides. Chromatographic profiles of elements are generally analogous to those obtained with a Fractogel column, but better chromatographic resolution of separated species was achieved so that slight differences between samples were revealed. Estimated molecular weights of major phosphorus species in soybean flour and common white bean seed extracts are 6 and 3.6 kDa, respectively, whereas those of minor phosphorus species in both samples are 0.7 kDa. Traces of phosphorus were also detected in the high molecular weight region (130 kDa). Chromatograms of P, Ni, Cu, Zn and Mo compounds in both extracts are similar but not identical. Molecular weights of major Cu and Zn species are ∼1 and 0.4 kDa for soybean flour and white bean seeds, respectively. In cases of Mn, Fe, Co and Se, the element profiles of soybean flour and white bean seed extracts are significantly different.

The role of trace elements in uraemic toxicity

Although most research on uraemic toxicity has focused on the retention or removal of organic solutes, subtle changes in the concentration of inorganic compounds are also of importance because these compounds may have significant clinical consequences. Potential clinical implications include increased risk of cancer, cardiovascular disease, immune deficiency, anaemia, renal function impairment and bone disease. In uraemic patients, the most important factor affecting trace element concentration is the degree of renal failure and modality of renal replacement therapy. Accumulation of trace elements in haemodialysis patients has resulted from dialysate contaminated with aluminium and strontium. Several trace elements have been implicated in the decline of renal function. These include arsenic, cadmium, copper, germanium, lead and mercury. In uraemic patients, aluminium, cadmium, chromium, lanthanum, strontium and zinc have been shown to accumulate in bone. In addition to substantial evidence linking aluminium to renal osteodystrophy, studies have also implicated cadmium, iron and strontium in bone disease. Studies using a rat model of chronic renal failure have demonstrated an association between lanthanum accumulation and mineralization defects characteristic of osteomalacia. Investigations of arsenic accumulation in animal models have demonstrated that speciation of trace elements potentially may alter toxicities of trace elements accumulated in uraemic patients. Conversely, the presence of uraemic toxins may also alter the uptake and toxicity of certain trace elements. Although research in uraemic patients has focused primarily on total concentrations of trace elements, the evolution of both inorganic and organic species should be considered separately.

Retention of trace elements using fly ash in a coal gasification flue gas

AbstractA fly ash sample was used as sorbent for trace element (As, Se, Cd and Zn) species at high temperatures in flue gases from coal gasification. The influence of temperature (550 and 750 °C) and gas composition (with and without H2S and HCl) on retention capacity was evaluated. It was concluded that this fly ash is an efficient sorbent for retaining As, Se, and Zn compounds in the gas phase from a coal gasification flue gas, retention capacities varying with temperature and gas composition.© 2002 Society of Chemical Industry

Determination of chlorine in coals by ion chromatography

Environmental legislation has had significant impact on coal utilization, especially coal combustion for power generation, in limiting emissions of potentially hazardous materials to the environment. For the most part, such emissions derive from the inorganic constituents in coal. However, as such legislation becomes ever more encompassing, it has increased the need to understand better the behavior of the inorganic species in coal processing to ensure, in part, that such legislation is not unduly burdensome. Consequently, it has led to significant development of new models for the behavior of inorganics in coal combustion and a complementary enhancement of many analytical methods for determining inorganics in coal.In this paper, analytical methods for inorganics in coal are reviewed on three fronts: (i) methods for determining elemental concentrations; (ii) methods for determining the mineralogy of coals; and (iii) methods for determining modes of occurrence (speciation) of trace elements in coal. The concept of association with respect to mineral–maceral and mineral–mineral occurrences is also discussed. Where possible, comparison of different analysis methods has been made by reference to data on well-characterized suites of coals, such as the Argonne premium coal samples.Incremental enhancements will continue to be made in analytical methods for elemental concentrations; however, major improvements are needed in the other two areas. There is a great need to verify and corroborate by direct speciation methods, the many inferences made by indirect methods regarding trace element speciation. Also, improvements in the measurement of mineral association and its integration into the coal mineral analysis by means of the computer-controlled scanning electron microscopy (CCSEM) would be a significant advance. Accurate determinations of both association and coal mineralogy would lead to significant and much-needed refinements of models for the behavior of inorganics in both coal cleaning processes and coal combustion.

Interaction of chemical species with biological regulation of the metabolism of essential trace elements.

Variations in the chemical speciation of dietary trace elements can result in the provision of different amounts of these micronutrients to the organism and might thus induce interactions with trace-element metabolism. The chemical species of Zn, Fe, Cu, and Mn can interact with other components of the diet even before reaching the site of absorption, e.g. by formation of poorly soluble complexes with phytic acid. This might considerably modify the amount of metabolically available trace elements; differences between absorptive capacity per se toward dietary species seems to be less important. Homeostasis usually limits the quantities of Zn, Fe, Cu, and Mn transported from the gut into the organism, and differences between dietary species are largely eliminated at this step. There is no homeostatic control of absorption of Se and I, and organisms seem to be passively exposed to influx of these micronutrients irrespective of dietary speciation. Inside the organism the trace elements are usually converted into a metabolically recognizable form, channeled into their biological functions, or submitted to homeostatically controlled excretion. Some dietary species can, however, be absorbed as intact compounds. As long as the respective quantities of trace elements are not released from their carriers, they are not recognized properly by trace element metabolism and might induce tissue accumulation, irrespective of homeostatic control.

Control of Trace Elements in a Gasifier Hot Gas Filter: A Comparison with Predictions from a Thermodynamic Equilibrium Model

A thermodynamic equilibrium model has been used to make predictions of the speciation of trace elements in the fuel gas from a gasifier. In contrast with previous studies of this nature, experimental data was available to enable the validity of these predictions to be tested. Although Be, Co, Cu, V, and Zn had been detected in the fines collected by the hot gas filter, no significant amount of these elements was predicted to be in the form of gaseous-phase species, and this was confirmed by the experimental data. The elements As, B, Cd, Pb, Sb, and Sn were all predicted to form a larger amount of gaseous species than measured experimentally. Some of these differences may be attributable to the current unavailability of thermodynamic data for the more complex minerals and adsorbed species that may be formed. Refinement of the predictions for As and B by inclusion of specific minor/trace element interactions with Ni and Ca, respectively, gave a better agreement with the experimental data. Thermodynamic equilibrium modeling is a useful tool for providing a qualitative understanding of trace element behavior, and for formulating strategies for their control.

Trends in certified reference materials for the speciation of trace elements.

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.

Upgrade of the x‐ray fluorescence beamline at HASYLAB/DESY

A new x-ray optical system for the fluorescence beamline L at HASYLAB is currently under construction and its commissioning phase will start early in 2001. Basis elements of the optical system are a double single-crystal — double multilayer monochromator, x-ray mirrors and capillary optics. The high-resolution Si crystal monochromator is designed for microscopic x-ray absorption near-edge structures (µ-XANES) experiments in fluorescence mode for laterally resolved speciation of trace elements. Broadband excitation by the multilayer monochromator will be used in total reflection x-ray fluorescence (TXRF) experiments and microscopic x-ray fluorescence analysis (µ-XRF). An energy range of 2.4–80 keV will be explored by the monochromator system, giving access to the K-edges of elements with 16 < Z < 79. A set of plane and cylindrical x-ray mirrors allows a high-energy cut-off at 12 and 30 keV, respectively and optional prefocusing. The microfocus is generated by monocapillaries and polycapillaries. The performance of different monocapillary optics in the synchrotron beam was measured in polychromatic and monochromatic modes. Copyright © 2001 John Wiley & Sons, Ltd.

Upgrade of the x‐ray fluorescence beamline at HASYLAB/DESY

AbstractA new x‐ray optical system for the fluorescence beamline L at HASYLAB is currently under construction and its commissioning phase will start early in 2001. Basis elements of the optical system are a double single‐crystal — double multilayer monochromator, x‐ray mirrors and capillary optics. The high‐resolution Si crystal monochromator is designed for microscopic x‐ray absorption near‐edge structures (µ‐XANES) experiments in fluorescence mode for laterally resolved speciation of trace elements. Broadband excitation by the multilayer monochromator will be used in total reflection x‐ray fluorescence (TXRF) experiments and microscopic x‐ray fluorescence analysis (µ‐XRF). An energy range of 2.4–80 keV will be explored by the monochromator system, giving access to the K‐edges of elements with 16 &lt; Z &lt; 79. A set of plane and cylindrical x‐ray mirrors allows a high‐energy cut‐off at 12 and 30 keV, respectively and optional prefocusing. The microfocus is generated by monocapillaries and polycapillaries. The performance of different monocapillary optics in the synchrotron beam was measured in polychromatic and monochromatic modes. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Acoplamento cromatografia gasosa - espectrometria de absorção atômica em estudos de especiação: uma revisão

This review presents an updated overview of the trace element speciation by gas chromatography coupled with atomic absorption spectrometry.

Ultrafiltration behavior of major ions (Na, Ca, Mg, F, Cl, and SO 4) in natural waters

Aquatic colloids, including macromolecules and microparticles, with sizes ranging between 1 nm to 1 μm, play important roles in the mobility and bioavailability of heavy metals and other contaminants in natural waters. Cross-flow ultrafiltration has become one of the most commonly used techniques for isolating aquatic colloids. However, the ultrafiltration behavior of chemical species remains poorly understood. We report here the permeation behavior of major ions (Na, Ca, Mg, F, Cl, and SO 4) in natural waters during ultrafiltration using an Amicon 1 kDa ultrafiltration membrane (S10N1). Water samples across a salinity gradient of 0–20‰ were collected from the Trinity River and Galveston Bay. The permeation behavior of major ions was well predicted by a permeation model, resulting in a constant permeation coefficient for each ion. The value of the model-derived permeation coefficient ( P c) was 0.99 for Na, 0.97 for Cl, and 0.95 for F, respectively, in Trinity River waters. Values of P c close to 1 indicate that retention of Na, Cl, and F by the 1 kDa membrane during ultrafiltration was indeed minimal (<1–5%). In contrast, significant (14–36%) retention was observed for SO 4, Ca, and Mg in Trinity River waters, with a P c value of 0.64, 0.82, and 0.86 for SO 4, Ca and Mg, respectively. However, these retained major ions can further permeate through the 1 kDa membrane during diafiltration with ultrapure water. The selective retention of major ions during ultrafiltration may have important implications for the measurement of chemical and physical speciation of trace elements when using cross-flow ultrafiltration membranes to separate colloidal species from natural waters. Our results also demonstrate that the percent retention of major ions during ultrafiltration decreases with increasing salinity or ionic strength. This retention is largely attributed to electrostatic repulsion by the negatively charged cartridge membrane.

Chiral speciation of trace elements: approaches to the speciation of selenoaminoacid enantiomers in biological samples

The “state of the art” of chiral trace element speciation, that is, the recognition of the particular enantiomer in which the trace element sought is occurring, is given here. The importance of such studies and speciation information is highlighted. Recent advances and trends in the development and applications of analytical approaches for chiral speciation of trace elements in biological material are also reviewed. A comparative overview is given of existing selenoaminoacids chiral speciation methods, based on hybridization of an adequate chiral separation technique (e.g., high-performance liquid chromatography, gas chromatography or capillary electrophoresis) coupled on-line with selenium specific detection by inductively coupled plasma mass spectrometry (ICP-MS). Applications of these hybrid methodologies, reported so far in the literature, to selenoaminoacids chiral speciation in biological real samples are also reviewed.

Summary paper of the EC Network on trace element speciation for analysts, industry and regulators—what we have and what we need

Summary paper of the EC Network on trace element speciation for analysts, industry and regulators—what we have and what we need

Identification of chemical species of some trace and minor elements in mature breast milk

The chemical speciation of trace elements of environmental, toxicological, clinical and nutritional interest was undertaken in breast milk, with the goal of ascertaining the chemical forms of Ba, Bi, Cd, Cu, Li, Mg, Mn, Mo, Pb, Sr, Tl and Zn. At the same time, the analytical potential of size-exclusion chromatography (SEC) coupled with quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) for the purpose of chemical speciation was further explored. Breast mature milk from 30 mothers living in Turin (Italy) and its surroundings was analyzed. Total element concentrations obtained in this study were similar to those reported for human milk in other countries. As regards speciation data, these pointed to the presence in human milk of specific ligands, such as enzymes and citrates, with strong affinity for some elements, presumably increasing the bioavailability of the elements themselves. The experimental approach and the analytical method developed in this study appear adequate for the purpose and can therefore be exploited for similar investigations.

Trace element speciation at cell membranes: aqueous, solid and lipid phase effects.

Biological interest in trace element speciation has tended to be polarised in very different ways according to the concerns of the investigators. Much of the ecological interest has centred on the effects of metal ions in the external environment with the "free metal ion model" dominating discussions of potential toxicity. By way of contrast biochemists have been much more concerned with the stereochemical and kinetic aspects of specificity in metal protein interactions in the cytoplasm. Separating these two sets of interests are the membrane biophysicists whose studies have concentrated on the channel concept. All three groups have tended to ignore speciation onto the solid phase. In the overall biological context, trace element speciation in the cell is more concerned with kinetics and the evolution of specificity of interaction between diverse ligands than with the conditions for equilibrium.